Sound recording system and aperture



April 26, 1949. A. R. ULMER 2,463,142

SOUND RECORDING SYSTEM AND APERTURE Filed Be t). 22, 1945 I i 21 k Azzzevfl 044/542,

Arm/awn Patented Apr. 26, 1949 2,468,142 SOUND REGOBQDINGYS'YSTEM E APERT .tllfredtR; Ul-memDumont, N 51, assignor to 'ltadio :Corporation 0t America, asconponationi oflDela ware ApplicationDecerhbeh 22, 1945, Seflal N o.-' 636;.968 6IClaims. (Cl. 179 -,100.3)

.fIhis.inventionrelatesto-sound recording equipmentand. particularly. to a method of and means tor. recording eithera negative or a direct positive sound record with. the same recorder.

IIn Dimmick lSMPatent; N0. 2,311,159 of February .16, .1943, a. method of and means for recording, a directpositiveitype of sound record is disclosedandclaimed. ".This patent. describes a system wherein; theilight.issoiimpressed on the film that after the normal development thereof, thetrack or. record, is.in the form produced by printing from the usual negative. There are many advantages?in thefdirect recording of such a record withoutgoing'. through the printing operation-step. as pointed out in the above-mentioned patent. There are also advantages in the recording ofa negative, andithe present invention discloses a system whereby the recorder can be very rapidly adjusted so'that'it will record either a negative or a direct positive record, according to the setting of the modulating element.

Dimmick'U. '8. application, Ser, No. 629,294, fi led'November'l7/I945, a combination negative anddirect PQSitive'recording.system has been disclosed and. claimedjthis'Dimmick system utilizing-achevron-shape'd aperture and a plurality of 'slits' in the slit .mask, the modulating element, such as a galvanometer, being adjustable to impress the li ht beam at either of twopositionson the slits, these. positions "determining whether. or not" the system will record a negative or a direct positive record.

The present invention .is directed to a recording system offthis, type, but one wherein, bya novelshape aperture, only a single .slit in the slit mask is necessary instead. of; theplurality. of slits.-

The same indicating. monitor system may be used as; disclosed andclaimed. in Dimmick U. S. applic a. t1on,"Ser..No. 629,295, "filed November 17, 1945.

The principal object of the invention, there- 'fore,'is to facilitate" the recording of film sound records.

Another object oi the invention is. toprovide an improved recording method for the. productionof either-ne ative or direct. positivesoundtracks.

Kfurther"object of the invention is to provide an improved system for recording either a negative or adireqtrositive sound track.

iAfij'St inlfurtheIZObjBCt of the invention is to provide a sound recording. system which may be changed from a negative recording to a direct positive "recording system, or vice versa, with a minimum-modification of thesystem.

A still further objector the inventionis-to provide ran improved recording. mask aperture.

.2 whichtpermitsthe recording of eitherha negative record or :a, direct positiverecord.

. Although the novel features which arebelievedto be characteristic :ofmthis invention will be point d out With.;-particu1aritvi the. ap nded claims, the ma-nner' ;of-, its; organization and the mode of its operation, will;v be better understood byvref erring to ..the. tollowingdescription. read, in,

conjunction "with the accompanying drawings, forming .a part hereofyinWhich:

:Fig. .1 .is .a .diagrammaticrview ;of .a .recording system embodyingtheinvention and .Fig. .2 -is..a view of theislitsmask of Eig. 1. showing the light beamsnperimposedthereon innegag tive recording position.

. Referring now :to -.t he= drawings; in i which the ame numerals-reefer: likeelements, the output of a microphonejzisf dvinto fanramplifier 6, and then directly ovenconductorsil to;=a;g alvanometer 8. The output oiamplifier s-ialso fed to a noise reduction amplifier. to -an :then. over conductors H to the galvanometer g, it being; well under-. stood that the galvanometer mirror- [2 is. vibrated both in accordance with. the instantane ous values of the sound waves.andtthe-envelope.or average value of thessoundwaves. Theremainingportion of the recording. system includes a light source La collectinglens. l-5 ,.-a mask plate I6, and a lens 18, together .witlr a lens 20, g, .s1it mask plate 2|, a lens. 2 3,.and;=a.film 22. In such asys; tem, light from. the laanp I4 is formed into a light beam shaped byathesaperture. 24-inthe mask 5, then projecteduon -.th e mirror I2.of the galvanorneter -8. from which-.itis. reflected to theslit mask 2!, thelight emerging-througha slit '25; being impressed-on thefilmill, as will'be described hereinafter.

Referring now to.Fig.:2 ;;an elevational view of the slit maskll, witha single slit 26: therein, is shown with a light -beam.30 'in;-shaded lines positioned thereon'for recording-a negative record. The. light beam may be. so positioned-by ad-. justment of the galvanometert on: the pivot-33 with the .handtscre-w.-32. This. position corresponds to a fifty percent modulation point, and-is the rest position before. noise. reduction is-applied. By turning the screw 32;:theggalvanometerwmay be rotated slightly so. that. therestposition of the light beamtll is as shown by the;dotted linesi36, at which position'a directpositive record will'be recorded.

In the above-identifiediDimmick application. Ser. No. .629,294 ,:.-filed November 117-, 1945, the manner 1 and 1 means of 'gxproducing: .the -difierent.

' types,of:records:areexplai-ned in detail. iltwwill:

'3 be noted that the shape of this aperture differs from that shown by Dimmick in that at the points or lines indicated at 34 and 35 along the slit 26, the lower edges of the beam are made parallel with the vibration of the light beam, or perpendicular to the slit, and are then continued outwardly parallel with the lower edges of the aperture. The upper edge of the aperture or light beam corresponds to the lower edge. The lines 34 and 35 permit the proper longitudinal aligning of the light beam along the slit.

As pointed out in the Dimmick application, the no-signal position of the light beam 30 on the slit would be such that only the tip portion of the beam passes through the slit to provide the usual bias line. The light beam is then vibrated by both the instantaneous values and the average values of the sound waves being recorded, the average position of the beam with respect to the slit being moved downwardly in accordance with the amplitude of the sound waves. Thus, at one hundred percent modulation, the light beam would vibrate between the points 34 and 35 on the slit 26, and would extend no further even at overloads of approximately one hundred percent because of the length of the sides of the aperture parallel with the direction of vibration of the light beam. It is obvious that the light striking the film with this type of modulation would produce the usual bilateral negative record, since the central exposed portions of the film would be opaque and the remainder, transparent.

Now, if the galvanometer is adjusted or rotated by the screw 32 so that th light beam assumes the position shown by the dotted lines 35, light will pass through the ends of the slit and over its entire length, except for fifty percent of the distance between points 34 and 35. Now, when noise reduction is applied, light will pass through the entire length of the slit, except for a narrow section at the center, to form the bias line. Thus, as far as densities and types of records are concerned, the results are the same with the present type of aperture with a single slit as with the Dimmick system employing a pair of offset slits to get the additional exposure for the direct positive record. As in the Dimmick system, the application of noise reduction is in the same direction and of the same amount regardless of the type of record being recorded. The present aperture is simple to construct, and avoids the making of multiple slits.

Referring again to Fig. 1, it will be noted that in the mask l6, two vertically elongated apertures 38 and 39 are shown. Light from either one of these apertures according to the position of the galvanometer 8 will be reflected by a mirror 4| on the slit mask 2| to a mirror 42, then upwardly through a projection lens 43 to a mirror 4-4, and then to a monitor card 46. Because of the reflections, the images of these apertures will be horizontal, as shown by the rectangles 52 and 53. On the card 46, is a line 48 to indicate fifty percent modulation of the light beam, and lines 48 and 55 to indicate one hundred percent modulation, the rectangular beams of light moving horizontally with the vibrations of mirror l2. When the galvanometer 8 is adjusted so that the light beam is in the position shown at 30 in Fig. 2, the rectangle 53 will be illuminated, and when the light beam is in the position shown by the dotted lines 35 in Fig. 2, the rectangle shown in the dotted lines 52 will be illuminated. In the rectangle 52, the word positive is printed, and in the rectangle 53, the word negative is printed. Thus, the operator not only will be able to adjust the bias of the system and observe the extent of modulation during recording, but will be able to observe whether the system is adjusted to record a direct positive record or a negative record. This monitoring system is disclosed and claimed in Dimmick copending U. S. application, Ser. No. 629,295, filed November 1'7, 1945.

I claim:

1. A sound recording system adapted to record either a negative or a direct positive sound record comprising a slit mask having a slit therein for passing light to a film in accordance with the position of a light beam on said slit mask an aperture mask having an aperture adapted to form light into a chevron-shaped beam having symmetrically receding sides, said receding sides being broken at predetermined points from the apex of said chevron, the receding sides at said broken points being connected by sides perpendicular to said slit, means for vibrating said beam parallel with the direction of said sides and perpendicular to said slit, and means for adjusting said vibrating means to position said beam on said slit mask so that the maximum light passing through said slit extends only over a length of said slit corresponding to the perpendicular distance between said sides perpendicular to said slit.

2. A sound recording system adapted to record either a negative or a direct positive sound record comprising a slit mask having a slit therein for passing light to a film in accordance with the position of a light beam on said slit mask, an

aperture mask adapted to form light into a chevron-shaped beam having symmetrically receding sides said receding sides being broken at predetermined points from the apex of said chevron, the receding sides at said broken points being connected by sides perpendicular to said slit, means for vibrating said beam parallel with the direction of said sides and perpendicular to said slit, and means for adjusting said vibrating means to position said beam on said slit mask so light passes through the end portions of said slit up to said broken points at all times during vibration of said beam.

3. A sound recording system comprising a light source, an aperture mask, vibrating means for a light beam formed by said aperture mask, a slit mask having a slit for passing light to a film in accordance with the position of said light beam on said slit mask, and means for adjusting said vibrating means to position said light beam on said slit mask in either of two positions, said aperture mask forming said light into a symmetrical chevron-shaped beam having receding.

upper and lower sides over the full width of said beam, said sides being broken at a predetermined distance from the apex of said sides and connected by sides perpendicular to said slit.

4. An aperture mask in a sound recording system, said mask having an aperture therein for forming light into a beam symmetrical about a vertical axis, said beam having two sides parallel with said vertical axis and top and bottom said light beam passing through the aperture in said mask, a slit mask having a single slit therein for passing light to film in accordance with the position of said light beam on said slit mask, said beam having a chevron shape with outer ends perpendicular to said slit and separated by a distance equal to the length of said slit, the upper and lower edges of said beam being at an angle to said slit and broken near the ends of said beam, said broken edges being joined by ends perpendicular to said slit, and means for adjusting said light beam on said slit mask so that only a portion of the lower edges of said light beam intersects said slit during the vibration of said light beam by said vibrating means.

6. A sound recording system comprising a light source, an aperture mask, means for vibrating said light beam passing through the aperture in said mask, a slit mask having a single slit therein for passing light to film in accordance with the position of said light beam on said 6 slit mask, said beam having a chevron shape with outer ends perpendicular to said slit and separated by a distance equal to the length of said slit, the upper and lower edges of said beam being at an angle to said slit and broken near the ends of said beam, said broken edges being joined by ends perpendicular to said slit, and means for adjusting said light beam on said slit mask so that only a predetermined portion of the upper edges of said beam intersects said slit during vibration of said light beam by said vibrating means.

ALFRED R. ULMER.

REFERENCES CITED UNITED STATES PATENTS Name Date Hanna Dec. 26, 1933 Number 

